You're piling on massive amounts of attributes, making your app almost impossible to read and figure out the transitions. Anything complex is going to become a tangled pile of nodes and code. It would take anyone but the original designer a long time to puzzle out what exactly is going on and figure out the workflow, unless there's also a ton of HTML comments in there too.
You have attributes that should just be classes with CSS (overflow: hidden prevents scrolling, not sure why you need lj-no-scrolling), you have html elements that actually need to have attributes to define their neighbours, and you're just overloading your HTML with a bunch of extra baggage that doesn't need to be there.
Look at your parallax example. A 30KB library, a bunch of superfluous divs, and a ton of extra attributes you need to try to figure out have successfully replaced "background-attachment: fixed". The sliding divs could be done so much more clearly with just a bit of javascript that tracks "current frame" and hides them all then shows the next one when you click the button. The ZoomUI is admittedly pretty, but I feel like you could do it much easier with just a click event that expands the frame via changing the classes on it, rather than all the extra baggage and divs and wrappers you need to make that work. The animations are pretty, but not worth the extra baggage it takes to use them.
It's a neat toy, but I can really only see it being usable by people who are inherently terrified of javascript and will do anything to avoid it. And even then they'd only need the simplest of use-cases, and they'd need to make sure it wouldn't be on something that would need updates, because I wouldn't want to have to come back to a project with this in 6 months.